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  1. NuclearNerd

    Custom Design Ball Thrust Bearing - Where to start?

    That's the source, yes. Page 18 talks about 4200 MPa as the static load limit from ISO 76-1987. The limit for austenitic stainless would of course be much less. The plan *is* to limit the load to something like 0.05 of the basic rating of an equivalent carbon steel bearing. I have somewhat...
  2. NuclearNerd

    Linear screw actuator

    I can't see from your sketch where the thrust loads from the lead screw will be transferred to the frame. Depending on the design of this thrust bearing, it could be a significant additional source of torque.
  3. NuclearNerd

    Custom Design Ball Thrust Bearing - Where to start?

    The numbers are looking a lot better using rollers rather than balls (lower Hertz stress for a given diameter). Keeping the contact stress below 200 MPa, I figure a 1/2" diameter x 1/2" long dowel pin could hold ~ 90 N (20 lbf). I can build an arbitrarily large diameter bearing, so squeezing...
  4. NuclearNerd

    Custom Design Ball Thrust Bearing - Where to start?

    With due respect, it seems to me that you are grossly underestimating the engineering,experience and precision that goes manufacture of into modern rolling bearings. I don't mean to minimize. I would dearly love if there were a commercially available solution for my application. Unfortunately...
  5. NuclearNerd

    Custom Design Ball Thrust Bearing - Where to start?

    Just pick up the phone I wish it were that simple. Bitter experience tells me that most companies are not interested in engaging on a small custom job, even if I'm willing to pay a premium. If you know otherwise, maybe you can point me to a willing company? You are really limiting the...
  6. NuclearNerd

    Custom Design Ball Thrust Bearing - Where to start?

    I need to spec a rolling-element thrust bearing in a fairly corrosive environment. Unfortunately I can't seem to find anything commercially available (400 series stainless won't work). I am considering making our own thrust bearing. It should be easy to manufacture a cage from 304SS (just a...
  7. NuclearNerd

    roy mech

    Thanks for the notice. Sorry to hear about that. Roy's site is one of the best (free) resources on the web for mechanical engineers. Our profession would be better off if we each contributed a fraction of what Roy did to the commons.
  8. NuclearNerd

    Internal Gear Contact Ratio Chart?

    Thanks tbuelna. I was hoping that the internal gear pair would have so much more load-sharing (at least 2-3x that of an external gear pair) that it would compensate for the extra support requirements for the internal gear. (I was imagining something like a belt drive, but with a fixed...
  9. NuclearNerd

    Internal Gear Contact Ratio Chart?

    So much for that brilliant idea. Thanks Dinjin!
  10. NuclearNerd

    Internal Gear Contact Ratio Chart?

    Thanks Dinjin. I looked at using the rack figures, but for the concept to work, it needs to show 2 or 3 x less bending strength than an equal thickness external spur gear. If you have a spreadsheet available, can you plug in the following ratios and let me know what you get for contact ratio...
  11. NuclearNerd

    Internal Gear Contact Ratio Chart?

    I am considering the design of a lightweight gearbox. I was hoping that by using an internal-external gear pair, I could get away with a much thinner gearset than I would with an external-external gear pair for the same torque. However I have not been able to find a good online reference for...
  12. NuclearNerd

    17-4PH corroded after EDM. Fix by Passivating?

    Right, it is only surface blushing now (no pitting), but it's only been submerged for a few months. The expected life is many years. I'll try the pickling route.
  13. NuclearNerd

    17-4PH corroded after EDM. Fix by Passivating?

    Hi all I've run into a new problem. We often spec 17-4PH for hardened parts that must stay operate in a fresh water environment. For the first time, I machined the part using EDM before heat treatment (to H1025). After immersion, the EDM surface shows significant corrosion, as shown in the...
  14. NuclearNerd

    looking for a COTS battery power pack with all the trimmings

    Telecomguy is on to something. After I googled "DC UPS" and "telecom", I came up with these two products which might be ideal (I still have to read the specs in detail): Pheonix Contact Siemens
  15. NuclearNerd

    looking for a COTS battery power pack with all the trimmings

    Without a full set of specs, I'm leery about using power tool batteries or consumer power packs. Neither specify their maximum discharge current, and in the case of power tool batteries the manufacturers won't warrant their use in anything but their own tools. The marine power pack lead looks...
  16. NuclearNerd

    looking for a COTS battery power pack with all the trimmings

    Hi there I'm a mech eng, so this is veering outside my expertise. I'm in the process of designing a portable material handling device for a customer. The device will need to be powered by a large battery (24v, 40a, 10 amp hours). I've done some preliminary research, and it looks like I'll...
  17. NuclearNerd

    How thick can I cut a beam from a thin card without L-T-Buckling?

    It's for fun. The mechanism is part of a large toy I want to build. I will probably do some experimentation, but I'd like to understand the structural equations so that I can minimize the number of wasted attempts. prex: thanks for the analysis. I need a bit of time to go through your...
  18. NuclearNerd

    How thick can I cut a beam from a thin card without L-T-Buckling?

    Yes, the flat strip, thanks. I took your advice and stopped looking for a dimensionless solution, and started playing with real numbers. I used the LTB formula presented in the American Wood Council's design guides: http://www.awc.org/pdf/tr14.pdf to find the critical moment Mcr where...
  19. NuclearNerd

    How thick can I cut a beam from a thin card without L-T-Buckling?

    Here's an interesting problem for you. I'm trying to make a mechanism consisting of a deck of laser-cut thin plastic sheets. Each sheet will have a beam cut into one edge, as shown in the attached sketch. The mechanism works by bending each of these beams in the deck independently. Ideally...
  20. NuclearNerd

    Idler that engages/disengages w/ direction change

    old-fashioned ratcheting clutches are generally smaller than sprag or roller clutches for the same torque capacity. If you are really Macgyvering it, you can cut apart a ratcheting screwdriver or socket wrench. It sounds like MikeHollaran is describing the reversing mechanism on a VCR...

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